Mapping the Response: The Rasuwa Flood
On August 26, 2026, a glacier collapse triggered a flash flood down Nepal's Trishuli and Bhote Koshi corridor. Within a day, volunteer mappers around the world were digitizing buildings and roads from satellite imagery to help responders on the ground. This tracks that real response, day by day, alongside the real, still-rising toll it responded to.
Scale bar in the bottom-left corner. To measure real distance: click the ↦ ruler icon (top-left, below the zoom buttons), then click points along the path you want to measure, the running distance updates as you go. Double-click, or click the last point again, to finish. Shift-click a point to delete it; Ctrl-click the last point later to keep extending the line. Click the ruler icon again to turn it off, or the × button to clear your measurements.
The flow path drawn on the map connects real, confirmed points (the glacier collapse origin, Timure, Syabru Besi, Trishuli Bazar) in geographic sequence down the valley. It's a straight-line approximation between those points, not a precisely traced flood path. Both task grids show as 100% mapped because that reflects real work already done, not full confidence in it: validation, the second review pass that checks accuracy, is still well behind on both projects. Copernicus's official damage count (240+ buildings destroyed, 32 damaged) covers only the areas its analysts have assessed so far, not the full corridor.
The valley itself, before and after
Real Sentinel-2 satellite imagery, cloud-masked and composited from actual clear passes, not a single day's snapshot. Scroll to zoom, drag to pan, and use the slider to compare.
Black/transparent areas are real gaps, not missing design: no cloud-free satellite pass covered that spot in the given window yet. The "after" side is thin because the flood only just happened; it fills in as more satellite passes come in over the following days and weeks.
This map has the same scale bar and ruler tool as the map above: click the ↦ icon (top-left, below the zoom buttons) to measure a real distance across the imagery, click to place points, double-click to finish.
The reported toll, by day
Each bar is exactly what was reported as of that date, not smoothed or backfilled. The toll kept climbing through this entire window as search and rescue continued.
What actually happened
Methodology
Mapping response: HOT Tasking Manager projects #63069 (buildings) and #63102 (roads), both live campaigns under the "2026 Nepal Floods" activation. Task grids and completion stats pulled directly from HOT's production API.
Toll figures: each snapshot is cited individually to its own source and timestamp (Kathmandu Post, Nepal Police, Nepal's National Disaster Risk Reduction and Management Authority), not drawn from a single running tracker, since no two trackers agreed exactly and the real number was moving daily.
Map context: named settlements, rivers, and the glacier collapse origin point (Langtang Lirung) geocoded individually against OpenStreetMap and cross-checked against news reporting of the affected corridor.
Data pulled August 2026, while search and rescue operations were still active. Figures here will already be out of date by the time you're reading this; check the cited sources directly for anything current.
References
Humanitarian OpenStreetMap Team, NAXA, & Open Mapping Hub Asia-Pacific. (2026). Nepal Floods 2026 mapping activation [Tasking Manager campaign]. tasks.hotosm.org
Copernicus Emergency Management Service. (2026). EMSR927: Flood in Nepal [Rapid mapping activation]. mapping.emergency.copernicus.eu
Nepal National Disaster Risk Reduction and Management Authority, via ANI News. (2026, August 28). Death toll reaches 538, 977 still missing as rescue teams race against fresh flood threat in Nepal.
Kathmandu Post. (2026, August 26). Update: Rasuwa flood death toll climbs to 95 as dozens remain missing.
OpenStreetMap contributors. (2026). Settlement, river, and place data for Rasuwa, Nuwakot, and Dhading districts, Nepal.